The Applicant has previously described a system enabling users to access information from a computer system via a printed substrate e.g. paper. This system has been termed a Netpage system by the Applicant. In the Netpage system, the substrate has a coding pattern printed thereon, which is read by an optical sensing device when the user interacts with the substrate using the sensing device. A computer receives interaction data from the sensing device and uses this data to determine what action is being requested by the user. For example, a user may make make handwritten input onto a form or make a selection gesture around a printed item. This input is interpreted by the computer system with reference to a page description corresponding to the printed substrate.
It would be desirable to print Netpage-enabled substrates even if a source document is Netpage-unaware, in the sense that the document was generated without the intention of being printed with a position-coding pattern and being made interactive.